 in a given area and then guesses how many are lost when a habitat shrinks overestimates its loss by a big factor. The fact is we don't know how many species are extinct or go extinct naturally. Most are unknown microorganisms and the only identified species to have gone extinct since 2000 is a type of mollusk. Just the Facts is a presentation of CFACT. For more information, visit us on the web at cfact.org. That's c-f-a-c-t dot o-r-g.